"linear measure, one-twelfth of a foot," late Old English ynce, Middle English unche (current spelling c. 1300), from Latin uncia "a twelfth part," from unus "one" (from PIE root *oi-no- "one, unique"). An early Anglo-Saxon borrowing from Latin; not found in other Germanic languages. Transferred and figurative sense of "a very small amount, small quantity" is attested from mid-14c. As the unit of measure of rainfall from 1845. Sometimes misdivided in Middle English as a neynche. Every inch "in every respect" is from early 15c. For phrase give him an inch ... see ell.